Certain concrete and/or cinder block walls are made without mortar between the blocks. For example, concrete or cinder block walls in coal mines often are made without mortar. When no mortar is used, a coating over the surfaces of the wall may be used to add strength and integrity to the wall and/or reduce air flows through the wall.
Other substances, such as wood, iron, rock, minerals, coal and various plastics, used to support roofs, form ductwork, extend or form vertical surfaces or walls, or ceilings, also require coatings for fire retardant insulation against fire damage as well as to maintain or enhance the strength and integrity of the structure.
Typically, such coatings for concrete and/or cinder block walls are made of compositions containing water soluble silicates, water, clay and fiberglass. These compositions dry very slowly, particularly when the coating is very thick. The surface normally dries forming a silicate skin which then retards the drying. Further drying produces a thicker skin which further slows the drying. Attempts to increase the drying speed of the coating have resulted in cracking of the coating, which causes the coating to be ineffective as a sealant. The coating is less effective when cracked because it then imparts less flexural strength to the concrete block wall and allows air flows through the wall.
A further problem with these coatings is that the fiberglass in the coating material is an irritant to skin and eyes which causes the coating material to be difficult to handle.
A further problem with coatings for vertical surfaces is that many coatings suffer from sag when applied to the surface by spraying since the coating must contain enough liquid to have a sprayable consistency.
Thus, there is a need in the art for a sprayable sealant composition which can impart strength to a vertical surface and/or ceiling, will dry relatively quickly, is not irritating to handle and will provide a fire retardant insulation to the member coated.